In an effort to conserve power and fuel because of the recent shortages thereof, some of the prior art thermostats were provided with various and sundry schemes for limiting the maximum heating and cooling set point temperatures thereof.
In one of the prior art thermostats, such as that shown in U.S. Pat. No. 4,078,601 for instance, the heating and cooling temperature ranges were established by the manufacturer, and the temperature selector was manually movable between such ranges through an "off range". Of course, as the temperature selector was moved through the "off range", it actuated a switching mechanism for placing the thermostat in the proper operating mode depending upon whether the temperature selector was being manually moved toward the cooling temperature range or the heating temperature range thereof. At least one of the disadvantageous features of the above discussed prior art thermostat is believed to be that while an operator might have desired to manually select an increased heating set point temperature or a decreased cooling set point temperature, there was always the possibility of inadvertently moving the temperature selector into the "off range" of the thermostat.
In another of the prior art thermostats, such as the thermostat disclosed in U.S. Pat. No. 2,729,719 for instance, adjustable stops, such as set screws or the like, were located in the temperature indicating plate of the thermostat for motion limiting or abutting engagement with the temperature selector thereby to define maximum and minimum heating set point temperatures of the temperature selector. Of course, while this thermostat was provided with adjustable stops for preselecting the maximum and minimum heating set point temperature, it is believed that one of the disadvantageous or undesirable features of such thermostat was that it was operable only in a heating mode.